The present invention relates to a random noise detecting system and method for a double sideband (DSB) amplitude modulation communication system.
In a conventional random noise detecting system as shown in FIG. 1, a high-pass filter 2 is used to detect a high frequency component (including no modulating signal component) in the detection output of an amplitude modulation detector circuit 1, thereby to detect the amount of noise present in the signal.
With this method, in a case such as in a tuner where band limitation is effected, it is difficult to completely separate the modulating signal and the noise from the AM detection output. In order to sufficiently separate the noise, it is necessary to increase the bandwidth. However, increasing the bandwidth lowers the performance of the tuner.